Abstract: Compositional Variations in Formation Fluids and their Relation to Fluid Flow in Devonian to Upper Cretaceous Sediments of South Central Alberta

The objective of this research is to examine whether the observed distributions in hydraulic head values and variations in the chemistry of fluids are consistent with flow models proposed for the Western Canada Sedimentary Basin (WCSB). The study area is south central Alberta and the units of interest are the Devonian through to Cretaceous aquifers. The study aims to establish recent and paleo-flow pathways by integrating hydrological, geochemical and geological data sets. The results will be compared to flow systems predicted by flow models for the WCSB. The distribution of the flow pathways will then be utilized in determining the nature of and the extent to which waters and their dissolved constituents interact with the surrounding rock mass and hydrocarbon accumulations. This unique approach has only recently become possible with reactive transport modeling where high quality databases are critical in parameter identification and justification. By modeling water-rock interaction, the potential for porosity and permeability reduction and/or enhancement, which has considerable economic implications for hydrocarbon exploration, can be utilized in assessing flow pathways and compartmentalization. Regions that exhibit a strong potential for cross-formational flow may be recognized through variations in chemistry and stable isotopes, this can prove significant in hydrocarbon exploration as it can open up potential plays in units overlying proven source rocks and established reserves. As well, in the WCSB Paleozoic waters tend to be rich in sulfate, and in overlying Mesozoic reservoirs introduction of sulfate rich waters at subcrop edges or through cross-formational flow may lead to bacterial sulfate reduction and souring of hydrocarbon reserves. 

AAPG Search and Discovery Article #90940©1997 AAPG Foundation Grants-in-Aid